Lean Manufacturing

requirements for mass customization?

- Elicitation: mechanisms for interacting with customer. (information on customer selections, physical measurments) - product design: suitable for customization - process flexibility: eliminate/reduce set-up. - logistics: tracking of the individualized items - all linked into an integrated system through information technology.

System definitions

- boundaries and scope - assumptions

make to stock:

- customer lead time is almost zero - product has a few options so that the demand can be forecast accurately. - positive inventory levels for a product is an order-wining criterion. Example: toothpaste

Assemble to order:

- customer lead time is less than manufacturing lead time - sub assemblies and parts for the final product are carried as inventory Example: cars

make to order:

- customer lead time permits the production to start on receipt of an order. - demand is unpredictable - engineering and design are completed and production process is proven. Example: new residential home

characteristics of continuous process/product focus?

- extremely high volumes and low variety: often single product - highly capital-intensive and automated - product layout: usually flow along conveyors or pipes - few changeovers required - long, continuous production runs enable to efficient processes - difficult and expensive to start and stop the process - typically high fixed cost but low variable cost - generally less skilled labor (example: oil refinery, steel plant, chemical plant.)

Problem definition

- goals and objectives - questions to be answered Why are we studying? Why are we studying it? What do we hope to learn? Who will act on the results?

characteristics of Mass (line) production?

- higher volumes - standard, repeat products - low and/or narrow skills - no set-ups, or almost instantaneous ones - higher levels of automation - product layout: a fixed sequence of operations (example: car production)

characteristics of batch processes?

- higher volumes and lower variety than for job shop - standard products, repeating demand. But can make specials - specialized, narrower skills - set-ups (changeovers) at each stage of production - process or cellular layout, predetermined planned routing

In process modeling, systems consist of:

- objects - processes that act upon entities to add value to the company's products. - events marking changes In The state of entities, resources, processes, or system overall - attributes ( or properties) of objects (part type, priority), processes, or the system overall. -relationships between objects - environment and boundary of the system.

Characteristics of project processes?

- one- off, complex, large scale, highwork content "products" - specially made, everyone customized - defined start and finish: time, quality and cost objectives - many different skills have to be coordinated - fixed position layout, resources brought to product (example: ship building)

engineering to order:

- the product is complex and engineering design is involved. - customer is willing to accept a long manufacturing lead time. Example: bridge, chemical plant

characteristics of job shop/process focus?

- very small quantities: "one-offs", or only a few required. - high degree of product flexibility - specially made. high variety, low repetition - facilitated are organized around specific activities or processes - general purpose equipment and skilled personnel -skill requirements are usually very broad - typically high costs and low equipment utilization - product flows may vary considerably making planning and scheduling a challenge.

Value stream mapping

- visualization of material/info flow - current/future state mapping to show existing conditions and future vision.

Boundry

-breadth (scope) of study - defined by interfaces to other systems - to much inside with make the model unwieldy and expensive -excluding too much may yield a trivial and unrealistic model

improved facility design:

-collocated machines, equipment, tools and people -compressed space -poka-yoke; means to keep the process from producing defects. -visual control: high visibility on the line, improved inter-process communications.

benefits of lean manufacturing:

-improved profitability - reduced costs - improved customer satisfaction - reduced throughput (flow) time - reduced lead times - higher quality - improved flexibility - improved employee morale

flexibility:

-produce different mixes or greater diversity of products quickly, without sacrificing efficiency at lower volumes of production.

Simulation Modeling Process

1. Problem definition 2. Project resource planning 3. System definition 4. Conceptual model formulation 5. Preliminary Experimental Design. 6. Input analysis 7. Model Translation to simulation language 8. Verify and validate model 9. Final experiment design 10. Experimentation (execute simulation) 11. Output analysis and interpretation 12. Optimization 13. Implementation and documentation.

four production strategies?

1. engineering to order 2. make to order 3. assemble to order 4. make to stock

What are the seven types of waste?

1. over-production 2. waiting time (including down times) 3. transportation 4. unnecessary processing 5. inventory 6. motion (operators) 7. Defects (scrap/rework)

5S? (Workplace Organization)

1. sort: sort out unneeded items 2. straighten: have a place for everything 3. shine: keep the area clean 4. standardization: create rules and standard operating procedures 5. sustain: maintain system and continue to improve.

Simulation modeling

A dynamic process model in which we can actually mimic a real system's operation in a computer-based model.

Model

A goal directed (or question oriented) abstraction of system.

System

A group or collection of interrelated elements which "cooperate" to accomplish some stated objective.

Process Modeling

A key in lean analysis.

Value stream

All actions, including value-added and non-value added, currently needed to bring a product through the two main flows essential to every product.

Concepts related to process modeling

Business process modeling Business process reengineering Value stream analysis

Simulation

Computer evaluation of various system alternatives (current/ future state)

How can products be made in continuous flow?

Cycle time for every operation in a process can be reduced to equal takt time.

the total time from release of a job at the beginning until it leaves a manufacturing/service system at the end.

Cycle time/flow time/sojourn time

Decomposition

Eg. Parallel identical assembly lines all making same product.

Objects

Entities (customers, parts, work orders) Resources (machines, tellers, mat handlers, workers)

Assembly line process modeling example

Entities: sub assemblies, finished product Resources: work stations, operators Processes: assembling, packaging, shipping Events: Machine idle, entity arrival Attributes: processing time, product type Relationships: flow between stations.

Data Model

Established assumptions about the attributes (parameters) of a model -what are the significant attributes of interest? - how can/do values of these attributes change?

Structural Model

Established assumptions about the operation of the system -define boundaries - ID entities - ID how entities interact ( use process modeling diagrams)

Process modeling diagraming tools

Flow charts, process diagram, activity diagrams, translation diagrams, value stream maps

Takt Time

Heartbeat of any lean system.

Process modeling

Identifies the entities that flow through a business or manufacturing system, and the sequence of processes (activities or tasks) that are applied to the entities.

System definition? Level of detail?

If too detailed model will be clumsy, expensive and error prone, if too simple model will be trivial, have unrealistic results, and no user confidence.

Aggregation Eg. Operator always does the same set of tasks for each work piece in sequence.

If we are not interested in the internal dynamics of a series of processed, we can often lump several detailed processes into one statistically equivalent process.

Continuous flow in its ideal state means...

Items are processed and moved directly from one processing step to the next.

a philosophy and operational strategy oriented toward achieving the shortest possible cycle time by eliminating waste and increasing the percentage of value-added time of total cycle time.

Lean Manufacturing

Decoupling Eg. Department divisions.

Looking for natural fault Lines to break up the system into sub-models (easier to work with)

Time between the order being released for manufacturing and the order being complete?

Manufacturing lead time

a delivery process through which mass-market goods and services are individualized to satisfy a very specific customer need, at an affordable price.

Mass Customization

has become an important ingredient of consumer purchasing decisions.

Mass customization

Simplification/reduction techniques?

Omission Aggregation Substitution Decoupling Decomposition

Omission

Omit detail (approximate) for no critical effects, and concentrate detail in significant effects.

Conceptual model formulation

Process model

Over production

Producing more, sooner, or faster than the next process requires.

what is the time taken to go from a product concept to a complete manufactured product?

Product development time

Project resource planning

Schedules, costs, personnel (skills, time), computer support (hardware and software)

Two parts of a simulation model?

Structural model and data model

Takt Time

The available production time divided by the rate of customer demand. Sets the pace of production to match the rate of demand.

Continuous flow

The most efficient way of turning materials into products.

Cycle times Down size Utilization WIP

The performance measures that will be used to analyze the system?

2 main flows essential to every product?

The production flow from raw material to the customer and the design flow from concept to launch.

Cycle time

The time needed to complete one cycle of an operation.

Time between the order placed by the customer and the order delivered to customer?

Total lead time

all of the activity and information streams that exist between the raw material supplier and the possession of customer.

Value stream

Tools for IDing waste?

Value stream mapping and simulation.

The dominant cost of manual production?

Worker's time in producing the item.

Resources

__________ represents a constraint that can be allocated to an entity or multiple entities.

Entities

___________ represents any person, object of thing whose movement through the system causes a change in the status of the system.

Attributes

___________ represents user-defined properties associated with an entity.

What is a "Manufacturing/Service system"?

a manufacturing system is a network of processes through which entities flow and whose purpose is to generate profit now and in the future.

External trends/demand/competitions dictates constraints on....

cost, time, and quality

waste minimization and short cycle time:

eliminate all activities that do not add value; eliminate safety nets; maximize use of scarce resources (capital, people, equipment, materials, land,..)

Variability reduction:

eliminate sources of variability in dimensions and time.

standardization:

make tested and proven methods standard.

Types of manufacturing systems?

manual production and mass production

What is the goal of manufacturing systems?

produce the product: - at a profitable cost - at a desired level of quality - with on time delivery

just-in-time materials/pull scheduling:

products are pulled from the consumer end, not pushed from the production end.

Quality of source, or perfect first-time quality:

pursue zero defects; reveal and solve problems at the source.

continuous improvement:

reducing costs, improving quality, increasing productivity and information sharing.

Cycle time=

set-up time+processing time+move time+ queue (waiting) time